Abstract : Direct Volume Rendering is one of the most popular visualization techniques. Although approaches such as ray-casting or slicing are fast and well-implemented on graphics hardware for regular and irregular grids, cell projection techniques are still time-consuming for large tetrahedral meshes. We propose improvements to the pipeline of cell projection techniques based on the SXMPVO [4] and the Projected Tetrahedra [8] (PT) algorithms. Specifically, we exploit new functionalities of the latest graphics hardware to remove bottlenecks in the sorting and rendering phases.